Dissertation
Dissertation > Medicine, health > Surgery > Of surgery > Cardiovascular and lymphatic system surgery > Cardiopulmonary bypass and resuscitation

Expression and Significance of HIF-1α on the Insulin Resistance during the Injury of Reperfusion of Ischemic Myocardium in Dog Undergoing Cardiopulmonary Bypass

Author ChangYu
Tutor LiangGuiYou
School Zunyi Medical College,
Course Thoracic and Cardiovascular Surgery
Keywords Cardiopulmonary bypass dog Ischemia reperfusion Insulin resistance HIF-1α
CLC R654.1
Type Master's thesis
Year 2011
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Objective:To study the expression and its significance of HIF-1αprotein content and total gene during myocardial ischemia-reperfusion in dogs with cardiopulmonary bypassMethods:18 healthy dogs were randomly divided into three groups including control group (no aortic cross-clamping), model group and DMOG intervention group (aorta was blocked for 60 min in the latter two groups). Before bypass, while the aortic opening, and after the aortic opening, in 15min,60min,120min, respectively, a left subclavian artery, coronary sinus blood, and the left ventricular myocardium were removed. This was followed by checking plasma glucose and calculating myocardial glucose intake and the net extraction rate of glucose through enzymatic measurement. Insulin and glucagon were determined by using radioimmunoassay. Plasma lactate concentration was determined via lactic acid enzymatic measurement. Plasma free fatty acids concentration was measured by gas chromatography. Thereafter the changes of insulin resistance (IR) at different time points were compared by suing relevant indicators. The changes in perioperative hemodynamics were also monitored. Myocardial HIF-1αprotein was examined by using immunohistochemistry on the removed left ventricular apical myocardium. The expression of myocardial HIF-1αand mRNA was examined by real time RT-PCR. Then image analysis was performed to analyse the changes of HIF-la protein expression.Results:(1) Cardiac glucose metabolism:After myocardial ischemia-reperfusion, plasma glucose was significantly higher in model group and DMOG intervention group, comparing with the control group and prior bypass CPB. The significant increase happened in various degrees, but reached peak in 15-60 min after reperfusion (comparing with control group, p<0.05 or p<0.01; comparing with before bypass, p<0.05 or p<0.01). Meanwhile myocardial intake and use of glucose experienced serious obstacles. Comparing with DMOG intervention group, the increase of plasma glucose level in model group is more serious and lasted longer (the difference between the two groups was significant, p<0.05 or p<0.01). Net myocardial glucose intake and net myocardial glucose intake rate were both zero after 15 min of reperfusion. In the following 60-120min after reperfusion,the model group and DMOG intervention group incurred different levels of glucose recovery, but didn’t restore to the levels before CPB.Comparing with the DMOG intervention group,the model group was slower and took longer in the recovery of intake amount and rate (the difference between the two groups was significant, p<0.05). After myocardial ischemia-reperfusion in 15-120 min, the Insulin Resistance Index was significantly higher in model group and DMOG intervention group,and then decreased significantly, but didn’t recover to the levels before bypass (comparing with control group, p<0.01; comparing with before bypass, p<0.05 or p<0.01). Meanwhile comparing with the DMOG intervention group, the ascension of Insulin Resistance Index in model group is more serious and significantly, took longer in the recovery (the difference between the two groups was significant, p<0.01). (2) Plasma insulin,glucagon, plasma lactate, plasma free fatty acid: Comparing with the control group and prior CPB, the model group and the DMOG intervention group had higher increase in plasma insulin, glucagon, plasma lactate, and plasma free fatty acids after myocardial ischemia-reperfusion. The increase were in various degrees, reached peak between 15 min to 30 min of aortic opening, then decreased gradually, didn’t return to the levels before bypass even at the point of 120min of aortic opening (comparing with control group, p<0.05 or p<0.01; comparing with before bypass, p<0.05 or p<0.01). Meanwhile comparing with the DMOG intervention group, the model group increased in higher degree, recovered more slowly and lasted longer (difference between two groups are significant, p<0.05 or p<0.01). (3) Total expression volume of myocardial HIF-la protein and mRNA:After myocardial ischemia reperfusion, the model group and DMOG group had significant increase in the total expression volume of HIF-1αand mRNA in various degrees, comparing with the control group and prior CPB. The increase is obvious after 15 min of blood perfusion (comparing with control group, p<0.01; comparing with before bypass, p<0.05 or p<0.01). Comparing with the DMOG intervention group, the model group had lower expression volume of HIF-1αprotein; however as the time progressing, its expression volume increased over the DMOG intervention group.After 120 min of reperfusion, comparing with the DMOG intervention group, the expression volume of HIF-la protein in the modern group had more obvious increase and the increase lasted longer (the difference between two groups are significant, p<0.05 or p<0.01). (4) Heart function:After 15 min of CPB myocardial ischemia and reperfusion, LVSP and±dp/dtmax decreased significantly in both model group and DMOG intervention group, but LVEDP increased significantly, then restored gradually, but didn’t recover to the levels before bypass (comparing with control group,p<0.05 orp<0.01; comparing with before bypass, p<0.05 or p<0.01). Comparing with DMOG intervention group, the model group had more obvious and significant decrease in LVSP and±dp/dtmax, and more obvious and significant increase in LVEDP. The recovery was much slower (the difference between two groups are significant,p<0.05 or p<0.01).Conclussion:After CPB ischemia, myocardial insulin resistance (IR) occurred. May the HIF-1αwas one of the markers for insulin myocardial resistance, It indicates that HIF-1αmay have acted as a molecules mechanism during myocardial IR occurred. DMOG may be through the impact on HIF-1αactivity to activate and stabilize the expression of HIF-1α, reducing insulin resistance in myocardial ischemia,alleviating myocardial injury during myocardial ischemia-reperfusion.

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